Turbine machines provide energy for a wide range of uses. A turbine machine comprises at least a rotatable shaft and a plurality of blades. In some applications the plurality of blades comprise a fan. Examples of turbine machines include turbofan, turbojet, turboshaft, and turboprop engines; gas turbine engines; and wind turbines.
The energy produced by a turbine machine is generally either electrical or mechanical. As one example, turbine machines are used to provide propulsion to an aircraft. A typical turbine engine comprises a compressor, a combustor, a high-pressure turbine, and a low-pressure turbine.
In some turbine machines, particularly in turbine engines used for aircraft applications, it is desirable to attach a nose cone upstream from the plurality of blades of the turbine machine. Nose cones are sometimes referred to in the art as “intake cones” or “inlet cones.” The nose cone can serve to reduce drag caused by the turbine machine, improve air flow to the plurality of blades, and avoid or limit damage potentially caused by impinging foreign objects. In supersonic aircraft, a nose cone is also advantageously used to slow the flow of air from supersonic flight speed to a subsonic speed before it enters the turbine machine.
In many applications a turbine machine must be balanced after the nose cone is mounted to the rotatable shaft and without removing the nose cone. Balancing a turbine machine, or the fan of a turbine machine, with the nose cone attached ensures that the turbine will not experience excessive vibrations during operation which can be caused by uneven weight distribution. Uneven weight distribution can be addressed during the balancing procedure by attaching the balance weights to the nose cone, fan, shaft, or other part of the turbine machine.
FIG. 1A is a partial sectional view of a nose cone 10 connected to a fan rotor 12 of an inlet fan of a gas turbine engine in accordance with conventional methods as described in U.S. Patent Application Publication No. 2011/0236217. The illustrated nose cone 10 comprises a flange member 14 which tapers to a leading cone tip (not shown) and a region proximate the trailing edge 16 having a radial thickness greater than that of the remainder of the flange member 14. A support ring 18 having an axially-extending flange 20 is connected to the fan rotor 12. A bolt 22 engages the trailing edge 16 of nose cone 10 to an axial member 24 and support ring 18. One disadvantage of the configuration shown in FIG. 1A and similar nose cone mounting configurations used in the art is that turbine balancing is difficult to perform because of the limited access to the plurality of bolts 22 which hold nose cone 10 to the fan rotor 12. Balancing is therefore typically performed with nose cone 10 removed from the fan rotor 12, and the re-connection of the nose cone 10 after balancing can introduce new weight imbalances.
In response to the shortcomings of the mounting configuration and nose cone 10 shown in FIG. 1A, configurations were developed to allow for turbine balancing to be performed with the nose cone 10 installed. FIG. 1B is a partial sectional view of a nose cone 10 connected to an inlet fan of a gas turbine engine as described in U.S. Pat. No. 8,540,492. As illustrated in FIG. 1B, a nose cone 10 comprises a flange member 14 which axially extends from leading cone tip (not shown) to a trailing edge 13. A radially thick mounting ring 26 is formed proximate the trailing edge 13. The mounting ring 26 defines a plurality of apertures 15 that are spaced apart about the circumference of the mounting ring 26. One or more of the apertures may include a recessed portion 17 for holding one or more balance weights 19. A fan rotor 12 is connected to retaining ring 28 having a mounting flange 30. A bolt 22 extends through an aperture 15 to connect nose cone 10 to the mounting flange 30. The bolt 22 also retains balance weight 19 within the recessed portion 17. As can be appreciated, the one or more balance weights 19 may be added or removed from recessed portions 17 without dismounting the nose cone 10 from the mounting flange 30.
Although the mounting configuration illustrated in FIG. 1B allows for turbine balancing without the need to dismount the nose cone 10, this configuration has its own drawbacks. In particular, it is preferred to manufacture nose cone 10 from fiber composite materials, also called filament wound composites. Typically a glass or carbon filament is wound around a rotating mandrel and, either contemporaneous with winding or after winding is complete, coated with a composite material resin which is then cured. The manufacture of components having varying thicknesses is difficult, time-consuming, and expensive. Thus, the nose cone 10 illustrated in FIG. 1B having an enlarged radial thickness at the mounting ring 26 is difficult, time-consuming, and expensive to manufacture.
While the present disclosure is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. It should be understood, however, that the present disclosure is not intended to be limited to the particular forms disclosed. Rather, the present disclosure is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure as defined by the appended claims.